The invention relates to a method and an apparatus for filling the bearing gap of a hydrodynamic bearing with a lubricant.
Hydrodynamic bearings, which are also referred to as fluid bearings, are used for example for a rotational support within high-precision spindle motors, utilized in hard disk drives and other high speed applications. In comparison with ball bearings, hydrodynamic bearings have higher running accuracy, quieter operation and much higher shock resistance (robustness). They operate virtually without any noise or wear, since, during operation at nominal speed, there is no direct physical contact with solid friction between the bearing parts rotating with respect to one another. Instead, there is a thin film of lubricant, for example a lubricating oil, located between the shaft and the shaft mount (bearing sleeve).
U.S. Pat. No. 5,778,948 discloses a method for introducing bearing fluid into a bearing having a fixed part and a rotating part. The fixed part and the rotating part are joined together in a high-pressure environment and subsequently brought into a low-pressure environment. In the low-pressure environment, the bearing fluid is introduced into a space between the fixed part and the rotating part. Next, this combination is brought back into the high-pressure environment in order to enable the bearing fluid to fill the space between the parts.
Another method for filling a fluid-dynamic bearing is disclosed in U.S. Pat. No. 6,305,439, in which a measured amount of oil is filled into a shaft opening and a shaft is subsequently inserted.
U.S. Pat. No. 5,601,125 discloses a further method for filling a hydrodynamic bearing with fluid.
U.S. Pat. No. 5,862,841 discloses an apparatus for filling a hydrodynamic bearing.